FAMILIAR British birds are under threat from a "bizarre" new Government law which could lead to an "irreversible loss" of wildlife, experts warned yesterday.

In its current form Sarah Durant warns the bill could seriously threaten the UK's biodiversity [GETTY]

A letter signed by 24 top scientists in the prestigious journal Nature slammed the Government's Infrastructure Bill which gives new powers to control or eradicate invasive or non-native species.

Invasive non-native species such as Himalayan balsam, Japanese ragwort, American crayfish and grey squirrels cost the country £1.8billion every year and often threaten native species.

But the academics, including experts from London Zoo, the RSPB and the John Muir Trust, and universities such as Cambridge, Oxford, London, York and Aberdeen, say the bill will classify barn owls and red kite as aliens.

If the bill is passed in its present form, it could lead to an irreparable loss of native biodiversity

Sarah Durant, of the Zoological Society of London

This would strip them of their legal protection putting them at risk if they get in the way of development plans.

In the letter Sarah Durant of the Zoological Society of London writes: "Proposed amendments to address these problems have been rejected. If the bill is passed in its present form, it could lead to an irreparable loss of native biodiversity."

The scientists said the Bill defines non-native species as those that are "not ordinarily resident in, or a regular visitor to, Great Britain".

This includes native species which have become extinct and species which could become established here in future thanks to a changing climate.

The scientists added: "It also includes species listed in Schedule 9 of the Wildlife and Countryside Act. That list contains native species, including some that have been reintroduced into the wild, such as the barn owl, capercaillie, chough and red kite.

"The legislation could also preclude future species reintroductions, a tool to counter biodiversity loss. The current definition has serious implications for wildlife management.

"Once a species is classified as non-native, it can also be classified as invasive and would therefore be subject to invasive-species legislation."

In a briefing paper for MPs, the RSPB described as "bizarre" the Government's plan to define as non-native species such as barn owls, corncrake, red kite, capercaillie and white-tailed eagles.

They are all native species which have been boosted by reintroduction schemes.

The RSPB said: "It would be perverse to create a legal definition of non-native that could apply to species that return to our shores after going extinct or that we wish to reintroduce in line with the recommendations of the Convention on Biological Diversity.

"This definition could create a bad precedent and would perhaps interfere with important reintroduction programmes if species that have disappeared can later be argued to be 'non-native'."

It said that species once native to the UK which have been reintroduced include the crane, great bustard, beavers and short-haired bumblebees.

It added: "There is an important principle at stake, that species that have gone extinct, often because of human actions, should not subsequently be considered 'non-native'."

The first bee-eater chicks reared successfully in the UK in 12 years have flown the nest, the RSPB revealed yesterday.

Bee-eaters - Europe's most colourful bird - are normally found near the Mediterranean and are rare visitors to the UK. But four chicks have been reared this summer by a pair on the National Trust's Wydcombe estate on the Isle of Wight.

National Trust ranger Ian Ridett said: "Around 3,000 people from around the UK have been rewarded with views of the adults catching bees and dragonflies.

"The question everyone is asking is, will they return next year? However it all depends on the weather and a degree of chance.

"With changing weather and climate, this is just one of the examples of birds and butterflies that are starting to spread north and west into the UK."

A Government spokeswoman said any issues raised would be considered during the parliamentary passage of the Bill. She said: "We want to use these control orders as a last resort to protect our wildlife and economy from invasive non-native species. They will not be used for species that are the subject of a legitimate reintroduction programme."